Problem Set 6
Principles of Cell Biology
1. Lysosomes are single membrane bound organelles that, by definition, stain positively with acid
phosphatase. They play a critical role in the ability of cells to degrade a variety of
a. Several drugs have been developed by companies like Genzyme (Sanofi) that can give
some relief to a variety of lysosomal enzyme diseases. Why is “replacement enzyme
therapy” an appropriate word to use for many of these therapies?
b. Chloroquine has been used to disrupt the lysosomes. How does this work and how is
chloroquine used today as a drug?
c. Hurler’s Syndrome and I Cell disease are both lysosomal storage diseases but they are
fundamentally different from each other. How is that the case?
d. You are investigating a possible newly discovered and very rare lysosomal storage
disease and need to identify its molecular defect. You hypothesize that the defect (never
before seen in any lysosomal storage disease) is a defective M6P receptor. How might
you use cell culture experiments to investigate this hypothesis?
e. Proteasomes were mentioned in class. How does the UPR (Unfolded Protein Response)
and ubiquitin relate to the large protein complexes that number 30,000/cell?
2. Autophagy was mentioned in class. While we have been aware of the normal function of
autophagy in most cells for decades, it has recently gained interest due to its implications in the
treatment of cancer.
a. Describe autophagy and how it differs mechanistically from heterophagy.
b. Why would a researcher want to manipulate autophagy in cancer cells?
3. Acetylcholine (ACH) is a neurotransmitter that works at the neuromuscular junctions.
a. What role does ACH have in the disease Myasthenia Gravis?
b. What types of drugs are used to treat Myasthenia Gravis and what is the mode of
4. Mitochondria were once thought to serve only one role – generation of ATP through
chemiosmotic oxidative phosphorylation. Now, however, we recognize that they appear to have
another role that is being targeted by both the large and small pharmaceutical industries as a
possible means to develop an improved paradigm to tackle cancer.
a. How is the generation of ATP different in the mitochondria versus in the cytoplasm?
b. How does the SGLT pump glucose into the cell and how can it pump glucose from the
extracellular environment into the cell against its gradient without the use of ATP?.
c. As presented in class, mitochondria appear to play critical roles in cell death. Under each
of the headings below, explain how each of the components is related to mitochondriamediated cell death.
Mitochondrial permeability transition pore
vii. Cytochrome c
5. Energy production is the primary responsibility of the mitochondria.
a. Describe the necessary structures and ingredients needed for the mitochondria to
produce ATP in the Citric Acid Cycle.
b. What is cyanide? How does cyanide affect the process of oxidative phosphorylation?
What would occur to an organism if cyanide is not promptly treated?
c. Researchers have developed several techniques for monitoring mitochondrial function,
including vital dyes. Name two vital dyes and how each specifically functions. Briefly
design an experiment which you could use these dyes to monitor mitochondrial activity.
6. Chloroplasts are the mitochondria of plants and other organisms that rely on photosynthesis for
the creation of ATP for energy.
a. What are the four stages of photosynthesis and give a brief description of each stage?
b. Purple bacteria are microorganisms capable of utilizing photosynthesis, but in a manner
different from plants. Describe this difference.
c. Describe the differences between carbon fixation and photorespiration. How is Rubisco
involved in each?
d. Cyanobacteria are now being considered as one of the future approaches to developing
renewable energy sources. What are the advantages of these organisms?
e. What is artificial photosynthesis?